What is Physical and Chemical Changes Class 7: Easy Explanation
By ConceptScroll Team · Published on 19 June 2026 · 3 min read
In Class 7 Science, understanding what is Physical and Chemical Changes is essential. These changes describe how substances transform either by altering their appearance or by forming new substances. This chapter from the NCERT syllabus explains these concepts with examples to help you grasp the topic easily.
Definition of Physical and Chemical Changes
Physical and chemical changes are two types of transformations substances undergo:
- Physical Change: A change affecting the form or appearance of a substance without changing its chemical composition. For example, melting ice into water.
- Chemical Change: A change that results in the formation of one or more new substances with different properties. For example, burning paper produces ash and smoke.
Understanding these definitions helps Class 7 students identify changes in daily life and in experiments.
Characteristics of Physical Changes
Physical changes have distinct features:
- No new substance is formed.
- Usually reversible.
- Changes in state, shape, size, or texture.
- Energy changes are often small.
Examples:
- Melting of ice
- Boiling of water
- Tearing paper
- Dissolving sugar in water
These changes do not alter the chemical identity of the substance, making them easy to reverse.
Want to test yourself on Physical and Chemical Changes? Try our free quiz →
Characteristics of Chemical Changes
Chemical changes involve:
- Formation of new substances.
- Usually irreversible.
- Energy changes can be significant (heat, light).
- Changes in colour, smell, or gas formation.
Examples:
- Rusting of iron
- Burning wood
- Baking a cake
- Vinegar reacting with baking soda
These changes show clear evidence of new substances being created.
Comparison Between Physical and Chemical Changes
Here is a table comparing physical and chemical changes:
| Feature | Physical Change | Chemical Change |
|---|---|---|
| Substance formed | No new substance | New substance formed |
| Reversibility | Usually reversible | Mostly irreversible |
| Change in properties | Only physical properties | Chemical properties change |
| Energy change | Small or none | Often involves heat/light |
| Examples | Melting, freezing, tearing | Burning, rusting, cooking |
This table helps Class 7 students quickly differentiate the two types of changes.
Worked Example: Identifying Change Types
Example 1: When water boils and turns into steam, what type of change is it?
- Boiling water is a physical change because water changes state but remains chemically the same.
Example 2: When iron nails get rusty, what change occurs?
- Rusting is a chemical change because iron reacts with oxygen to form a new substance, iron oxide.
These examples clarify how to classify changes in everyday situations.
Why is Understanding These Changes Important for Class 7 Students?
Knowing physical and chemical changes helps students:
- Understand natural and scientific processes.
- Perform experiments safely and accurately.
- Prepare for exams with clear concepts.
- Relate textbook knowledge to real-life phenomena.
The NCERT Class 7 Science textbook explains these changes with simple language and examples, making learning easier and exam preparation effective.
Frequently asked questions
What is the main difference between physical and chemical changes?
Physical changes do not form new substances, while chemical changes produce new substances.
Can physical changes be reversed?
Yes, physical changes are usually reversible, like melting and freezing.
Give an example of a chemical change from daily life.
Rusting of iron or burning wood are common examples of chemical changes.
Does dissolving sugar in water cause a chemical change?
No, dissolving sugar is a physical change because no new substance forms.
How can you tell if a change is chemical during an experiment?
Look for signs like colour change, gas release, or formation of precipitate.
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